Ik vraag me af of zij thuis is.
English: I wonder if she is at home.
In Dutch, 'bijzinnen met of' are subordinate clauses that start with 'of'. They are used to introduce indirect yes/no questions or to express doubt or alternatives.
Use this structure when you want to report a yes/no question or when you are unsure about something. It is common after verbs like 'weten', 'vragen', 'twijfelen', or 'denken'.
Ik vraag me af of zij thuis is.
English: I wonder if she is at home.
We weten niet of het morgen regent.
English: We don't know if it will rain tomorrow.
Kun je zien of de winkel open is?
English: Can you see if the shop is open?
Hij twijfelt of hij mee zal gaan.
English: He is unsure if he will go along.